The purpose of this pilot is to study the relationship between highly prevalent parasitic infections and mental and motor development in Puerto Rican children living in rural areas of the Island. We propose the hypothesis that under conditions of environmental impoverishment among children within populations, where energy-protein deficiencies are endemic, there is an inverse relationship between incidence of parasitic mobidity and measures of motor, sensory, cognitive and language development as measured by the Bayley Scales for infants and the Kaufman assessment Battery for older children. In addition, measures of protein-calorie intake and anthropemetric indicators will be analyzed in relation to the incidence of parasitism and its effects on nutritional status and behavior. The sample will consists of 120 children affected by parasites and stratified by age, sex, and socio-economic status. An additional sample of 120 normal children will be tested and used as a control group. Multiple regression analysis using social-environment factors, nutritional and morbid status as predictors of test scores in the cognitive domain will be analyzed to detect either combined or independent relationships for each group of children. Also, the presence of contributing environmental factors and socio-cultural variables will be studied by case studies, including home visits and field work. The value of this research rests on the fact that possible biological correlates are being controlled to test the hypothesis of malnutrition and its detrimental effect on intellectual development across different stages of development. Performance site for this research will be Inter American University of Puerto Rico Metropolitan Campus. The present research promises an immediate positive impact through cooperation between the department of biological sciences parasitology and psychology and with local officials of public health and health care delivery systems in rural areas of the Island.